Apart from this Red Hat also shared Technology Previews within each release. Functionality that is not yet supported, but available for testing purposes:

FCoE (Fibre Channel over Ethernet)

More kernel tracepoints for systemtap

ext4 filesystem support

gcc 4.4 and new glibc malloc

CIFS DFS support

samba3x and ctdb support for use with GFS

SPICE X11 drivers (future feature-rich display protocol)

Clustering with KVM hypervisor

Power LPAR support

If you have Red Hat Network entitlements you should have access to the RHEL 5.4 Beta and now is the time to report any issues you may find !

If you are looking for the RHEL 5.4 Beta ISO images, go to Red Hat Network, log in, click on Download Software, expand the RHEL5 channel for your architecture and go to the Beta channel. There you can find the RHEL 5.3 Beta ISO images.

I was confused about it too. In fact I expected it to be in -155.el5 as well, much like kvm. But I noticed kvm comes seperately as kmod-kvm.

However, despite what Red Hat is announcing, I can't find FUSE or XFS either. Although I haven't checked the DVD myself yet.

Also, beware that Red Hat is not supporting XFS for every customer. They will only provide support for specific customers that are unable to use one of the other filesystems (ext3, ext4, gfs, ...) for their solution.